Known methods for the production of optically active ethyl 2-hydroxy-4-phenylbutyrate, which is one of 2-hydroxy acid derivatives represented by the formula (II), include chemical and asymmetric reduction of (R)-2-hydroxy-4-phenylbutyric acid (cf. Eur. Pat. EP 206993) and chemical synthesis comprising synthesizing (R)-2-hydroxy-4-phenylbutyric acid from benzylmagnesium chloride and optically active glycidic acid followed by ethyl-esterification (cf. Japanese Patent Laid-Open No. 212329/1987).
However the former method comprising the asymmetric chemical reduction cannot give a satisfactory optical purity of the product, while the latter one comprising the chemical synthesis is disadvantageous in that optically active serine, which is the starting material for the optically active glycidic acid, is expensive for industrial uses.
Furthermore, no process for the production of an optically active 2-hydroxy acid derivative represented by the formula (II) from a 2-oxo acid derivative represented by the formula (I) by taking advantage of the capability of asymmetric reduction of a microorganism has been reported so far.